The Nebra Sky Disk is an astronomical clock:
A Babylonian cuneiform script from the seventh century BC and the detective work of a Hamburg astronomer have solved the mystery of the Nebra Sky Disk: Rahlf Hansen deciphered a leap month rule that can be read from the 3600-year-old bronze disk.
With the rule, the lunar year and the solar year are resynchronized - the lunar year is slightly shorter than the solar year and therefore runs out of sync over time, with the rule on the disk the owners knew when they had to reset the lunar calendar by inserting a leap month.
It's quite amazing to consider that the disk is from the Bronze Age. And Babylonia and Saxony are not really close to each other (although the records are almost a thousand years younger, making the achievements of the disk's manufacturers even more interesting).